You already know how handy and effective your Voice Alert system can be. Now you can easily tie in any type of sensor to the Voice Alert. Use existing security system sensors or add a new magnetic switch or other sensor. Accepts either NO or NC contact closure. Since the Voice Alert's already a wireless system, this transmitter is all you need to use these additional sensors. Runs on a 9V battery for up to one year (alkaline) or up to 5 years with a lithium.